I started a sorority of bettas recently and shortly after they started dieing off. I had been keeping them in other tanks and divided areas before combining the bettas in this larger 16 gallon tank.

I've seen many other threads related to this, but it always turns into a thread about convincing the guy to buy a heater and do water changes and I miss the whole point about the disease?

I do water changes, about 50% weekly. The tank is a couple of months old now. It's planted. I has a 100 watt heater. It's only stocked with 5 false julii corydoras, 1 dwarf orange crayfish (CPO), and has also had 1 juvenile betta in a breeder box. The remains of the sorority of bettas in the tank is 1 cambodian female and 1 veil tail female. They were a few of my most docile bettas and are getting along very well. I would hate to lose them, its not easy to find docile females for a sorority.

I lost 2 fish to the pump impeller. They found a way to the back of the nano tank and it was a freak accident from there. I've since fixed that by covering the intake vents with foam. Never thought they could fit in there. Shortly after that incident I lost another betta. She initially showed signs of being sluggish and just hovering at the top of the tank. She wasn't clamped and looked normal. I did notice a small change in her mouth coloration (lighter) but it was hardly enough to think it looked too different. She died the next day. I now have another betta Ive since moved to another tank who is not moving hardly at all and her mouth is all white.

Do I have a fungus problem in my 16g? I think its what all my clues are pointing too, but I'm still quite new with keeping fish.

There's no point in saving this betta. She's too far gone and if I go by symptoms I've seen in a couple of the other bettas she will be gone in a few hours. It happend so fast and its usually down hill by time I notice the symptoms.

The big thing here is do I need to treat my 16 gallon to prevent problems with the current fish there?

Housing
What size is your tank? 16 gallons
What temperature is your tank? 8.0
Does your tank have a filter? Dual 3-stage (built into tank)
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes
What tank mates does your betta fish live with? 5 False Julii Corys & 1 CPO Dwarf Orange Crayfish

Food
What type of food do you feed your betta fish? Frozen Blood Worms, Frozen Brine Shrimp, Betta Pellets
How often do you feed your betta fish? Once a day

Maintenance
How often do you perform a water change? Once a week
What percentage of the water do you change when you perform a water change? 50%
What type of additives do you add to the water when you perform a water change? Prime

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Symptoms and Treatment
How has your betta fish's appearance changed? White mouth
How has your betta fish's behavior changed? Hovering at top not moving much
When did you start noticing the symptoms? After adding to tank
Have you started treating your fish? If so, how? No
Does your fish have any history of being ill? No were fine before moving tanks
How old is your fish (approximately)? < 8 months

So sorry that you have had fish loss and illness, Do you have access to a ammonia/nitrite test kit? It's very common for a newly set-up tank to have toxic levels of one or the other, and it causes what you have described.

I believe you have columnaris. It's also called white mouth disease and cotton mouth disease. It's a bacterial disease that kills very quickly and it can kill off a tank full of fish in a few days.

Treatment is tough with columnaris, and many time unsuccessful. You'll need to treat the whole tank, although treating the cories may be tricky as scaleless fish are sensitive to meds and you may have to treat them at half strength.

If it was me I would destroy the sick girl and quarantine the other one so that you can treat her at full strength. There are a few different meds you can try - there is a sticky thread in this forum with info and of course there is Google. I would do some research and see what meds you would be able to get locally since the disease spreads so fast. Also research the best way to treat the cories. You could wait and see if it spreads to the cories, but the best bet is to try to treat them now.

Honestly on other fishkeeping forums I'm on people will often destroy all their fish at the first sign of columnaris, tear down the tank, disinfect it and start over because it's so virulent. But it's worth a try at least to see if you can treat them. I have no idea about the crayfish.

The meds may kill off your beneficial bacteria so you may also have to deal with ammonia and cycling issues.

Your ph is a bit high. But a higher ph won't directly kill your fish but it will lead to stress making them more vulnerable to an infection and parasites. That may be what is happening to your fish, but I'm not quite sure.

To me it looks like mouth fungus,or Columnaris. Which is caused when fish are stressed by water quality, poor diet, and in result they become prone to bacterial infections. Columnaris enters the fish through the its gills, mouth, and even through small skin wounds. The disease can spread rapidly in nets, holding containers, food or any number of other means. It is highly contagious.

To treat a betta for this you can :Change water,Vacuum gravel (bacteria thrive on organic wastes) ADD AQUARIUM SALT(enhances gill function) Treat with copper sulfate,antibiotics and chemicals (Acriflavine, Furan, and Terramycin) Discontinue carbon filtration during treatment.

But I would suggest treating your bettas in a smaller tank because catfish are highly sensitive to salt.

So sorry that you have had fish loss and illness, Do you have access to a ammonia/nitrite test kit? It's very common for a newly set-up tank to have toxic levels of one or the other, and it causes what you have described.

I do test for that stuff as well as using an ammonia alert. I gave these readings above.

I believe you have columnaris. It's also called white mouth disease and cotton mouth disease. It's a bacterial disease that kills very quickly and it can kill off a tank full of fish in a few days.

Treatment is tough with columnaris, and many time unsuccessful. You'll need to treat the whole tank, although treating the cories may be tricky as scaleless fish are sensitive to meds and you may have to treat them at half strength.

If it was me I would destroy the sick girl and quarantine the other one so that you can treat her at full strength. There are a few different meds you can try - there is a sticky thread in this forum with info and of course there is Google. I would do some research and see what meds you would be able to get locally since the disease spreads so fast. Also research the best way to treat the cories. You could wait and see if it spreads to the cories, but the best bet is to try to treat them now.

Honestly on other fishkeeping forums I'm on people will often destroy all their fish at the first sign of columnaris, tear down the tank, disinfect it and start over because it's so virulent. But it's worth a try at least to see if you can treat them. I have no idea about the crayfish.

The meds may kill off your beneficial bacteria so you may also have to deal with ammonia and cycling issues.

Oh gosh your right, it's the plague... it is death...so sorry I have seen it wipe out an entire fish room in just days. I would never put that crayfish back into any tank ever again ever. thankyou wendyjo & lexyle for spotting it. I will now include you as one of the go to fish medics.